There is increasing evidence that glucocorticoids (GCs), primarily cortisol in humans and corticosterone in animals, can interact with drugs of abuse and influence drug-seeking and drug-taking behaviors. This study is designed to determine if the mood-altering effects of d-amphetamine are altered by pretreatment with hydrocortisone or placebo, followed by d-amphetamine or placebo, in randomized order under double blind conditions. Salivary cortisol levels will be obtained and correlated with subjective and behavioral measures. It is hypothesized that hydrocortisone will potentiate the subjective and behavioral effects of d-amphetamine. This protocol uses the services of the GCRC Core Laboratory only.